Vertical power transistors, in particular vertical MOS transistors, such as power MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors) or power IGBTs (Insulated Gate Bipolar Transistors) are widely used in industrial, automotive or consumer applications, such as power converter circuits, or load drive circuits for different types of loads, such as lamps or motors. Vertical power transistors include a semiconductor body and a load path extending in a vertical direction of the semiconductor body, so that load terminals (source and drain terminals) are located on opposite sides of the semiconductor body.
Usually, a gate terminal of a vertical MOS transistor is located on the same side of the semiconductor body as the source terminal. This is because, the source region and the gate electrode are usually located close to the surface region on the same side of the semiconductor body. However, there are applications in which it is desirable to only have the source terminal (source metallization) on one side of the semiconductor body and to have the drain terminal and the gate terminal on the opposite side. Having only the source terminal on one side of the semiconductor body is, e.g., beneficial in those applications in which the MOS transistor is employed as a low side switch that has the source terminal connected to a terminal with a low-side supply potential, such as ground. In this case, the source metallization can be directly soldered to a contact surface, such as a leadframe, connected to the low-side potential. When the low-side potential is ground, the leadframe can be directly mounted to a cooling element without providing an electrical insulation between the leadframe and the cooling element. This provides for an efficient cooling of the MOS transistor, in which most of the heat is dissipated close to the source region and, therefore, close to the surface where the source terminal is located.
There is a need to provide a vertical power transistor that has drain and gate terminals located on the same side of a semiconductor body and that is capable of withstanding high voltages in the off-state, in particular voltages of more than 100V.